The present invention relates to the field of flexible road joints of the type comprising a flexible material resulting from a mixture of granulates and binder, used to fill a trench formed in a road surface on a level with a gap between two structural elements supporting the surface covering.
Flexible joints of this type are used between successive sections of the deck of a bridge, for example, where the amplitude of gap movements (gusting wind) between these sections is not too high. They provide an economic solution and also ensure continuity in the driving surface and good acoustic comfort.
The compositions used to make such joints are more often than not based on a thermoplastic binder. By way of example, European patent 0 000 642 describes a flexible joint with a base of bitumen and rubber scrap as a binder whilst French patent 2 562 108 describes a joint made using a binder based on bitumen and an elastomer vulcanised with sulphur.
Binders based on two components have also become available, in which the flexible matrix is made by cross-linking products respectively incorporated in the two components. The advantage of these formulations is that they can be used at ambient temperature, which makes works easier to carry out.
Improvements in the materials used in the binder composition have made joints less sensitive to softening, which tends to give rise to ruts across the road surface. Striking a better compromise between the flexibility of the joint and its sensitivity to softening has meant that joints of this type can be used for works where exposure to gusting wind is likely to be higher.
However, the joint remains fragile when subjected to traction due to gap movement between the two adjacent roadway supports. The flexible material is at risk of tearing away from its support close to the edge of the surfacing, which reduces continuity in the road surface as well as the closure function of the joint. This risk is even greater if using this type of joint in even higher winds.
A main objective of this invention is to improve the behaviour of such a flexible joint when subjected to traction forces.
Accordingly, the invention proposes a method of forming a flexible joint between two sections of roadway, supported respectively by two contiguous structural elements, a roadway surface being formed by a surface covering applied on top of the structural elements and interrupted above a gap separating the two structural elements to form a trench of a width greater than that of said gap. In accordance with this method, a closure member covering said gap is placed in the base of the trench and granulates and a binder are poured into the trench which form a flexible material on curing. Before pouring in the granulates and binder, reinforcements are laid in the trench which are attached to the two structural elements at either end of the closure member, these reinforcements being perforated to allow at least some of the granulate mixture to pass through.
The reinforcements allow the joint to be reinforced in areas where the risk of tearing under traction forces is greatest. The fact that the reinforcements are perforated allows the granulates and binder to pass through the reinforcement from either side and into its midst. The resultant reinforcing effect is efficient.
In one particularly advantageous embodiment, the binder is made up of several components, preferably including a polyurethane, mixed and used at ambient temperature.
In specific modes of implementing the method:
each reinforcement has a convex portion resting on the bed of the trench;
each reinforcement has a first portion resting on the bed of the trench and a second portion applied along an end surface of the surface covering bordering the trench;
each reinforcement is a piece of unfurled metal;
in order to attach the reinforcements, holes are bored in the structural elements at the base of the trench, metal rods are inserted in these holes with their top ends left projecting so that they can be inserted through the perforated reinforcements and the top ends of the rods are folded down over the top of the reinforcements;
the closure member is coated with grease;
the closure member comprises at least two flexible sheets one on top of the other, which are disposed so that they overlap along the direction perpendicular to the gap separating the two structural elements, the side edges of the closure member, disposed substantially parallel with the gap, belonging to separate sheets.
One of the sheets is preferably disposed so that it covers the entire gap separating the two structural elements.
Another aspect of the invention relates to a joint for a flexible roadway between two sections of roadway respectively supported by two contiguous structural elements, a roadway surface being formed by a surface coating applied on top of the structural elements and interrupted above a gap separating the two structural elements to form a trench of a width greater than that of the gap. The flexible joint is located in the trench and comprises a closure member covering said gap at the base of the trench and a mixture of granulates and flexible binder. It additionally comprises perforated reinforcements, attached to the two structural elements at either end of the closure member and embedded in the mixture of granulates and binder.